COVID-19 is putting a strain on many sectors, including HVAC. Therefore, it is important we put our focus and attention to the following guidelines, as every action can impact the lives of many.
This is a summary of guidelines drawn by experts from REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations) to aid the sector and its attempt in reducing the spread of COVID- 19 and offer support to resume operations.
The aim of these guidelines is to provide HVAC professionals, facility managers, with information on how to operate and use building services during the pandemic. These guidelines will help with preventing the spread of COVID-19 with HVAC systems.
Small particles carried by airflow can travel long distances across rooms or extracted through air ducts of ventilation systems. Although currently there is no evidence for COVID-19 spreading this way, there is no data ruling out this possibility either. There is one indication that SARS-CoV-2 has been isolated from swabs taken from vents in rooms occupied by infected patients. Hence, we should implement the following suggestions as much as we can.
How to run building services during the COVID-19 pandemic
Increase air supply and ventilation
- Extend operation times
- Keep ventilation on 24/7.
- Ventilation systems of toilets should be on 24/7.
- Supply as much outside air as reasonably possible.
- Reduce the number of occupants and increase the air volume to reflect capacity.
When ventilation systems are not available, ventilate by opening windows
- Open windows, more than normal, even if this causes some thermal discomfort.
- It is important to keep windows open in different spaces in order to achieve cross flow throughout the building.
Humidification and air-conditioning have no practical effect
- COVID-19 is resistant to environmental changes and is only susceptible to humidity levels above 80% and at temperatures above 30 ˚C. These levels of humidity and temperatures are not attainable and acceptable in buildings for thermal comfort.
Safe use of heat recovery sections
- Rotary heat exchangers (including enthalpy wheels) should (temporarily) be off during SARS-CoV-2 episodes.
- If there are any suspected leaks in the heat recovery sections, pressure adjustment, bypassing can be an option to avoid a situation where higher pressure on the extract will cause air leakage to the supply.
No use of recirculation
- Virus particles in return ducts can re-enter a building. To avoid this, close the recirculation dampers.
- This may lead to problems with cooling or heating capacity, but it is more important to prevent contamination and protect public health than to guarantee thermal comfort.
- De-centralised systems such as fan coil units that use local recirculation should also be turned off to avoid resuspension of virus particles.
Duct cleaning has no practical effect
- Small virus particle would not deposit easily in ventilation ducts as they are normally carried out by the air flow.
Change of outdoor air filters is not necessary
- The size of a coronavirus particle is 80-160 nm (PM0.1), this is smaller than the capture area of Fine filters (capture efficiency 65-90% for PM1)
- SARS-CoV-2 particles also aggregate with larger particles which are already within the capture area of filters
- In the rare instance that the outdoor air has been contaminated, The outdoor air filters provide a reasonable protection for a low concentration and occasionally spread viruses in outdoor air.
- From the filter replacement perspective, normal maintenance procedures can be used.
- Clogged filters are not a contamination source in this context, but they may reduce supply airflow which has a negative effect on indoor contaminations itself. Thus, filters must be replaced according to normal procedure when pressure or time limits are exceeded.
Room air cleaners can be useful in specific situations
- To be effective, air cleaners need to have at least HEPA filter efficiency
- Devices that use electrostatic filtration principles (not the same as room ionisers!) often work quite well too.
These recommendations can only compliment the general guidance for employers and building owners presented in the WHO document ‘Getting workplaces ready for COVID-19’.
For more detailed information please refer to the REHVA documents and web pages below.
Please find below link to REHVA web page with guideline document and bibliography.
To download the Guide line please click the below link:
To download the Bibliography please click the below link: